1. Field of the Invention
The present invention relates to a fuel cell system.
2. Description of Related Art
There is known a fuel cell having a fuel cell stack formed by stacking a plurality of unit fuel cells (hereinbelow, referred to as “unit cells”). Each of the plate-shaped unit cells is formed by disposing a pair of separators on both sides of a membrane electrode assembly. The membrane electrode assembly is formed by sandwiching a solid polymer electrolyte membrane between an anode and a cathode.
In this fuel cell, hydrogen gas (anode gas) is supplied as fuel gas to a fuel gas passage, which is formed between an anode electrode and an anode-side separator. In addition, the air (cathode gas) is supplied as oxidant gas to an oxidant gas passage, which is formed between a cathode electrode and a cathode-side separator. Accordingly, the hydrogen ion generated at the anode electrode by a catalytic reaction transfers to the cathode electrode, permeating through the solid polymer electrolyte membrane, and electrochemically reacts with oxygen in the air, thereby generating electricity.
The fuel cell is constituted so that the generated electricity is outputted via an electrode provided at the fuel cell, and that no electricity leaks out from elsewhere, preventing a ground fault.
An example of such constitution, as shown in Japanese Unexamined Patent Application, First Publication 2008-130261, includes a contact prevention member which prevents contacts between the fuel cell and an insulating material surrounding the fuel cell, thereby preventing a ground fault between the insulating material and the fuel cell.
In the above-described fuel cell, during the electricity generation, a large amount of generated water is generated in the fuel cell, through the reaction of hydrogen and oxygen. Moreover, in a fuel cell equipped on a fuel cell vehicle, the amount of electricity generation varies along with the variation in the load applied to the fuel cell vehicle. In particular, when a large load is applied to the fuel cell vehicle, the electricity generation amount of the fuel cell becomes larger, and when a small load is applied to the fuel cell vehicle, the electricity generation amount of the fuel cell becomes smaller. In addition, when the fuel cell vehicle is driven at the maximum performance thereof, or the like, in the fuel cell, a high-load electricity generation is performed. On the other hand, in occasions in which the vehicle is reducing the speed, for example, when stopping at a traffic signal, the electricity generation amount of the fuel cell decreases abruptly.
Among those occasions, when the fuel cell vehicle is in the high-load status constitutively, the generated water generated in the fuel cell is blown out along with the gas which is continuously supplied into the fuel cell. However, when the fuel cell vehicle is in the low-load status, and the electricity generation amount of the fuel cell is reduced, the gas amount supplied into the fuel cell also decreases accordingly. As a result, there is a problem in that the generated water which had been ejected along with the reaction gas supplied to the fuel cell accumulates in the gas ejection channel without being ejected.
When the accumulated generated water within the fuel cell bridges the fuel cell and a external attachments of the fuel cell (e.g., a humidifier, a catching tank, or the like), there is a concern that a ground fault occurs in the fuel cell. In the case of such a ground fault in the fuel cell, there is a possibility of electricity troubles such as an excessive electric current passing though the fuel cell, or the like.
The present invention was made in view of the aforementioned circumstances: an object thereof is providing a fuel cell system which can prevent a generated water accumulation in a fuel cell stack, and preventing a ground fault in the fuel cell stack caused by such generated water.